1. Field of the Invention
The present invention relates to a lens adjusting device for a camera, and more specifically relates to a lens position adjusting device provided in a lens barrel for camera in which a lens group moves in an optical axis direction by a rotation of a manual operating ring provided on the lens barrel, wherein the lens adjusting device is configured to be capable of adjusting the position of the lens group in the optical axis direction with respect to the rotation position of the manual operating ring.
2. Description of the Related Art
A photographic lens barrel of a camera which is provided on a lens barrel with a focus ring (manual operating ring) and a zoom ring (manual operating ring) that are operated by the user to change the position of one or more movable lens groups provided in the lens barrel in an optical axis direction to thereby adjust the focus and the focal length of the photographic lens, respectively, is known in the art. Various mechanisms for changing the position of one or more movable lens groups by a rotation of the focus ring or the zoom ring have been proposed. Among such mechanisms, a mechanism wherein a cam ring provided in a lens barrel rotates via a rotation of a manual operating ring, and a lens frame which supports a lens group is provided integrally with a set of cam rollers (cam followers) which are respectively engaged in a set of cam grooves formed in a cam ring to convert rotational movements of the cam ring into linear movements of the set of cam rollers, i.e., linear movements of the lens group supported by the lens frame, is known in the art.
In the lens barrel having such a mechanism, it is necessary to perform an adjusting operation for precisely matching a position of the movable lens group in the optical axis direction with a corresponding rotation position of the manual operating ring. For instance, in a focus adjustment operation, upon the focus ring being turned to a specific one of a plurality of markings of the distance scale formed on the lens barrel, the movable lens group is adjusted so as to be moved to the corresponding position in the optical axis direction that corresponds to the distance represented by the specific one marking. A technique of adjusting the distance between the focus ring and a focus cam ring in the optical axis direction is known in the art as a technique of performing a focus adjustment operation for adjusting the rotation position of the focus ring and the position of the movable lens group in such a manner to correspond to each other. Namely, if the position of the focus cam ring relative to the focus ring in the optical axis direction is changed, the position of the focus cam ring in the optical axis direction varies even when the focus ring is rotated to the same rotation position thereof. To perform this adjusting operation, it is conventionally the case that one or more adjustment shims, each having a required thickness in the optical axis direction, is installed at the joint between the focus ring and the focus cam ring to be interposed therebetween so that the relative position between the focus ring and the focus cam ring can be adjusted by changing the number of the adjustment shims interposed therebetween. For instance, a conventional adjusting method for adjusting focus of a lens by installing one or more washers (which operate just like the adjustment shims) into a lens system is disclosed in Japanese Unexamined Patent Publication No. 2002-62466.
In the technique of adjusting a lens position by adjusting the relative position between two members in the optical axis direction using such adjusting shims, the amount of focus adjustment is limited to the thickness of one adjustment shim, or limited to the total thickness of adjustment shims in the case of using more than one adjustment shim. In either of these two cases, the amount of focus adjustment can only be varied stepwise. Additionally, when a plurality of adjustment shims are selectively used, the stepwise values available for focus adjustment cannot be changed continuously though the amount of focus adjustment can be varied. In addition, there is a limit to the reduction in thickness of the adjustment shim and there is a limit to the improvement in precision of the thickness of the adjustment shim, and accordingly, it is difficult to define fine adjustment settings. Therefore, there has been a conventional problem of it being extremely difficult to finely and continuously adjust the lens position with no positional error in each of the focus adjustment operation and the zoom adjustment operation that are usually carried out in the manufacturing process.